The present invention relates to an apparatus for use with blanks folded to a flat form for unfolding each blank into a tube of rectangular to square cross section and feeding the tubular blank to one of container bottom forming mandrels which is at rest at a feed station.
Conventional apparatus of the type mentioned include those comprising a magazine for accommodating a multiplicity of blanks as arranged side by side, transport means for delivering the blanks from a delivery opening of the magazine one by one and transporting each blank to a position on an extension of the axis of the mandrel, means for unfolding the blank from a flat folded form into a tube of rectangular to square cross section during transport by folding the opposed flat portions of the blank, a holder for holding the tubular blank on the extension of axis of the mandrel in alignment therewith movably along the extension, and a transfer assembly for transferring the blank from the holder to the mandrel. The transport means has a suction member for holding one of the four side wall panels of the blank thereto by suction. The unfolding means has an unfolding member which is fixedly disposed within the path of transport of the blank so as not to interfere with the side wall panel held to the suction member. During transport, another one of the four side wall panels not held by the suction member is brought into contact with the unfolding member and thereby bent, whereby a fold is formed on each of the opposed flat portions of the blank.
With the conventional apparatus described, the unfolding member is fixedly disposed in the path of transport of the blank, so that the opposed flat portions of the blank can not be bent beyond a limit and therefore fail to remain fully bent to form the fold. When the blank is further transported as held in the tubular form by being slidingly moved longitudinally thereof, the force acting to restore the blank to the flat form then acts against the sliding movement. This gives rise to the problem that the blank being transported will not be smoothly transferred from the holder to the mandrel owing to great sliding resistance. Furthermore, where the blank is made into a container, a neat corner will not be formed at the junction of the adjacent two side wall panels, hence another problem of a poor appearance as a commercial product;